Transferable GaN Enabled by Selective Nucleation of AlN on Graphene for High-Brightness Violet Light-Emitting Diodes

A transferable GaN epilayer is grown on an improved aluminum nitride (AlN)/graphene composite substrate. In this study, theoretical calculations using first-principles calculations based on density functional theory are carefully conducted to further examine the formation mechanism of AlN on graphene. AlN selectively grows on graphene via its optimal nucleation site, which leads to the selective nucleation of AlN on graphene via quasi-van der Waals epitaxy. Thus, an AlN composite nucleation layer is innovatively inserted between graphene and GaN, using the time-distributed and constant-pressure growth method by metal organic chemical vapor deposition. Moreover, a high-quality GaN epilayer can be grown while ensuring the successful exfoliation of GaN by overcoming weak van der Waals forces between the graphene and the epilayer. The as-fabricated violet light-emitting diodes (LEDs) deliver an ultrahigh light output power. This method demonstrates the possibility of achieving a high-quality vertical structure for LEDs and the ability to mechanically transfer to achieve flexible lighting.